The efficiency with which various tests, reactions, assays and the like in biology, clinical diagnostics, and other areas, has been greatly increased by adoption of parallel sample handling techniques. Specific examples include polymerase chain reaction (PCR) techniques, enzyme-linked immunesorbent assay (ELISA), enzyme immune assay (EIA), radio-immune assay (RIA), membrane capture assays, cell washing, enzyme assays, including receptor binding assays, and the like. In most of these cases, the samples can be processed in multiwell plates. One of the most common formats is a 96-well plate, where the wells are arranged in a matrix having 8 rows and 12 columns.
In an effort to increase efficiency even further, and to reduce manual repetitive tasks performed by laboratory technicians, a number of multi-sample handling tasks are being adapted for use with automated systems. Such systems typically employ multiwell plates for storing, reacting and/or analyzing liquid samples, and generally include a liquid-handling apparatus, which transfers fluid between selected containers and/or wells, and an automated plate handling apparatus to manipulate the multiwell plates containing the samples. Examples of automated systems include robots for automated assembly and thermal cycling of PCR reaction, luminometers, plate readers and the like.
Samples handled in an automated system may need to be heated and/or agitated at specific points during the processing cycle. Such operations typically require the wells containing the samples to be sealed. The seals usually need to be fluid-tight to prevent loss of sample fluid, particularly in cases where the contents of the wells are heated (creating a positive pressure in the well). Following such a heating and/or agitation step, the plates may need to be uncovered (e.g., to add other reaction components to the wells or to remove reacted samples). In many cases, such as when a heated plate has been cooled prior to opening, the cover may be positively adhered to the surface of the multiwell plate. During cover removal, this adhesion, which may be due to polymer adhesive effects or pressure effects due to escape of some gases during heating and negative pressure on cooling, may result in (i) a dislodging of the plate from the tray holder, (ii) a sudden plate movement which spills sample contents, and/or (iii) a splashing of well contents onto the cover and/or other wells.
Accordingly, it would be desirable to have a cover capable of effectively sealing the wells of a multiwell plate in an automated system. The seal should be effective to prevent loss of well contents during heating or agitation, yet be able to be released at will without disrupting samples contained in the wells, and without the use of unnecessary force or unduly complicated systems.